1. Field of the Invention
This invention relates to a novel chromanol glycoside and a method for the production thereof. More particularly, it relates to a novel water-soluble antioxidant resulting from bond of a sugar to a 2-substituted alcohol and excelling in chemical stability and to a method for the production thereof.
2. Description of the Prior Art
For a long time, the formation of lipid peroxide has been known as a cause for degradation of food in quality. It has been recently established that this substance in biological system has bearing on various diseases including arteriosclerosis aging, and cancer, for example. Thus, the development of an antioxidant which fulfills the function of repressing the formation of lipid peroxide induced by active oxygen has been attracting growing attention not only in the field of foodstuffs but also in the field of cosmetics, the field of medicines, and many other fields.
As naturally occurring antioxidants, tocopherols, gallic acid, ascorbic acid, glutathione, and .beta.-carotene have been known. 2(3)-tert-butyl-4-hydroxyanisole and 3,5-tert-butyl-4-hydroxytoluene which have been synthesized for the purpose of keeping foodstuffs from oxidation of lipid have been also known as antioxidants.
The tocopherols excel over the other antioxidants mentioned above in the ability to suppress oxidation. Thus, they have been finding extensive utility in the fields of foodstuffs, cosmetics, and medicines. Since this outstanding antioxidant activity of tocopherols is ascribed to the chroman ring, 6-hydroxy-2,5,7,8-tetramethyl chroman-2-carboxylic acid (hereinafter referred to as "Trolox") derived from tocopherol by the substitution of a carboxyl group for the isoprenoid side chain at the 2 position thereof has already found recognition as a commercial product. Besides, 2-substituted alcohols of tocopherols have been known.
Since the tocopherols are viscous oily substances insoluble in water, they cannot be used as solutions in the form of injections or oral medicines. Trolox and 2-substituted alcohols show extremely low solubility in water.
As means for vesting these compounds with the solubility in water, such methods as (a) addition of a surfactant, (b) coverage with cyclodextrin, and (c) chemical modification (esterification) by the use of a water-soluble compound are conceivable. The methods of (a) and (b) require a surfactant or cyclodextrin in a fairly large amount and, therefore, entail heavy adulteration of relevant compounds with an inherently extraneous substance as a serious problem. Actually these methods fail to impart fully satisfactory water solubility to the compounds (JP-A-61-21,184, JP-A-62-281,855, JP-A-62-226,975, JP-A-60-116,643, and JP-B-41-5,118). The method of (c) which consists in modifying the phenolic hydroxyl group at the 6 position with a water-soluble compound is fated to lower the antioxidant activity to a notable extent. The tocopherols and the compounds containing a chroman ring have the disadvantage of showing instability to heat and alkalis.
An object of this invention, therefore, is to provide a chromanol glycoside, a novel water-soluble antioxidant excellent in chemical stability and usable as a solution making use of the chroman ring of outstanding antioxidant activity, and a method for the production of the chromanol glycoside.